It is customary to verify the authenticity of a written signature by comparing the pattern thereof with a previously registered pattern of the same signature, which may be held in the files of, for example, a bank or frequently nowadays already written on a credit card.
Hitherto, this task has been carried out manually but there is a need for a rapid and economic system for automatic signature verification. One of the difficulties inherent in such a system is to find a way of carrying out this task which is feasible on a large scale and applicable to digital data process techniques. Moreover if a credit card is stolen, it is not difficult for a thief skilled in such matters to learn how to copy the signature on the card accurately enough to satisfy a shop assistant or bank teller. Clearly there is a need for a more secure method of verifying a signature. Such a method could include monitoring the actual speed and rhythm employed by the authentic signatory and comparing these with stored coded records of the correct shape, speed and rhythm. A thief would not normally know, and would be very unlikely to be able to reproduce, the speed and rhythm used by the owner of the signature. Moreover, in the event that the legitimate owner of the card was using it at, for example, a street cash dispenser, and was accosted by a robber he may not under coercion sign his name with the same rhythm as he would use customarily under more relaxed conditions.
Quite a part from the above considerations, it is also common knowledge that the same person may sign his name on different occasions with patterns which are distinctly different in detail, and yet to the trained eye and in particular to the writer himself, such different signatures can be recognized as having been produced by the same hand. It is believed that the rhythm with which a signature is written is more important than the precise pattern produced, because it results from a learned sequence of nerve impulses delivered to the muscles of the hand at a rate too fast to have been controlled consciously with visual feedback.